A tear or a crack in the thin lining of the anus is known as anal fissure. The crack in the skin can cause severe pain and bleeding during and after bowel movements. At times, the fissure can be deep enough to expose the muscle tissue.

Anal fissures are very common in young infants but then again, it can affect people of any age.

Causes of Anal Fissure
Fissures or tears are often thought to be caused by the overstretching of the anal mucosa beyond its normal capacity. This often happens when stools are hard due to constipation.
Once the tear happens, it causes muscle spasm in the anal sphincter muscle (muscles around your anus). This pulls apart the edges of the fissure furthermore. The spasm also reduces the blood supply to the area, thereby making it harder for the fissure to heal. This cycle, leads to the development of a chronic anal fissure.

Risk factors

Factors that may increase your risk of developing an anal fissure include:

• Constipation   that makes you strain to pass hard stool. 
• Prolonged diarrhea can cause an anal fissure to develop.

• Pregnancy or Childbirth can put pressure on your perineum (the area between your anus and vulva).
• Inflammatory bowel disease causes chronic inflammation of the intestinal tract, which may make the lining of the anal canal more vulnerable to tearing e.g.  Crohn’s disease.
•  Trauma to your anus through anal sex or through surgery.

Symptoms of anal fissure

Symptoms of anal fissure may include: 

• Pain during and after a bowel movement that can last for hours
• A visible tear or crack in the skin around your anus
• Streaks of bright red blood on stools or on the toilet paper after wiping.

Complications of anal fissure

Complications seen with anal fissures include:

• Pain, bleeding and discomfort
• The fissure fails to heal, requiring surgery
• Tear extends to the surrounding muscles
• Reduced quality of life